Add support for scientific

Closes haskellari#97

src/Database/PostgreSQL/Simple/FromField.hs

@@ -127,6 +127,7 @@ import qualified Data.Text.Encoding as ST
 import qualified Data.Text.Lazy as LT
 import           Data.UUID   (UUID)
 import qualified Data.UUID as UUID
+import           Data.Scientific (Scientific)
 
 -- | Exception thrown if conversion from a SQL value to a Haskell
 -- value fails.
@@ -315,6 +316,11 @@ instance FromField (Ratio Integer) where
     fromField = atto ok rational
       where ok = $(mkCompats [TI.float4,TI.float8,TI.int2,TI.int4,TI.numeric])
 
+-- | int2, int4, float4, float8, numeric
+instance FromField Scientific where
+     fromField = atto ok rational
+      where ok = $(mkCompats [TI.float4,TI.float8,TI.int2,TI.int4,TI.numeric])
+
 unBinary :: Binary t -> t
 unBinary (Binary x) = x
 

src/Database/PostgreSQL/Simple/ToField.hs

@@ -41,12 +41,14 @@ import qualified Data.ByteString.Lazy as LB
 import qualified Data.Text as ST
 import qualified Data.Text.Encoding as ST
 import qualified Data.Text.Lazy as LT
+import qualified Data.Text.Lazy.Builder as LT
 import           Data.UUID   (UUID)
 import qualified Data.UUID as UUID
 import           Data.Vector (Vector)
 import qualified Data.Vector as V
 import qualified Database.PostgreSQL.LibPQ as PQ
 import           Database.PostgreSQL.Simple.Time
+import           Data.Scientific (Scientific, scientificBuilder)
 
 -- | How to render an element when substituting it into a query.
 data Action =
@@ -172,6 +174,10 @@ instance ToField Double where
               | otherwise               = Plain (double v)
     {-# INLINE toField #-}
 
+instance ToField Scientific where
+    toField x = toField (LT.toLazyText (scientificBuilder x))
+    {-# INLINE toField #-}
+
 instance ToField (Binary SB.ByteString) where
     toField (Binary bs) = EscapeByteA bs
     {-# INLINE toField #-}